High-Content Clonogenic Survival Screen to Identify Chemoradiation Sensitizers

Purpose: The combination of cytotoxic chemotherapy with radiation therapy (CRT) has resulted in significant improvements in clinical outcomes for patients with many locally advanced unresectable cancers. Only a small proportion of patients achieve pathologic complete responses to CRT; combination of CRT with targeted agents offers the promise of further improving treatment responses. However, numerous clinical trials have failed to show an improvement in clinical outcomes with the addition of targeted agents. To increase the accessibility of our screening method and accelerate the pace at which novel combinations with CRT are identified and incorporated into standard practices for treatments, we report details on screening method optimization, data generation, and downstream data analysis. Methods: In part, the gap in translation to large, expensive, and ultimately unsuccessful clinical trials reflects the shortcomings of inconsistently designed, executed, and reported preclinical data on which these studies are based. In an effort to standardize the selection of agents for future clinical testing, we have designed, optimized and validated a high throughput, high content, clonogenic assay platform for step-wise progression of preclinical studies from in vitro to in vivo in non-small cell lung cancer and pancreatic ductal adenocarcinoma. Results: This highly stable in vitro method was standardized for identification of the most promising CTEP drugs that could best be combined with CRT from among as screen of multiple agents tested in an unbiased manner using 96-well plates. The methodology lends itself to seamless testing of multiple agents in a similar fashion allowing cross-comparisons, evaluation of CRT, or radiation therapy alone, and testing multiple concentrations of test agents sequenced at different times before and after radiation. The method identified Trametinib as a strong CRT sensitizer in KRAS-mutant non-small cell lung cancer and pancreatic ductal adenocarcinoma cell lines. This platform has enabled the screening and identification of several chemoradiation sensitizers.Conclusions: High throughput, high content clonogenic drug screening assay allows for the rapid identification of targets and agents to be translated to the clinic to help improve the effectiveness of current standard of care CRT in various solid tumors.